Effects of hydrogen peroxide treatment on pulp breakdown, softening, and cell wall polysaccharide metabolism in fresh longan fruit

Longan (Dimocarpus longan Lour.) is prone to pulp softening and pulp breakdown, leading to a loss of its nutrients including polysaccharides. ROS is one main factor affecting fruit quality. This work intended to explicate the influences of hydrogen peroxide, acting as a ROS, on pulp softening, pulp breakdown, and cell wall polysaccharides metabolism in longan fruit during storage. Contrasted to the control group, hydrogen peroxide-treated samples exhibited lower firmness, lower amounts of CWM, ISP, CSP, hemicellulose and cellulose, but higher breakdown index, WSP amount, expression levels of DlPG, DlPE, Dlβ-Gal, DlCx and DlXET and activities of their corresponding enzymes (PG, PE, β-Gal, Cx, XET). These results suggested that hydrogen peroxide reduced longan pulp firmness due to the increased gene expression levels and enzymes activities related to cell wall polysaccharide degradation to boost their decomposition, thereby led to the accelerated pulp softening and the expedited pulp breakdown of harvested longans.